Method of making perforated plates



P Z 1953 J. E. wooos ETAL 2,633,630

METHOD OF MAKING PERFORATED PLATES Filed July 6, 1945 2 Si-IEETS-Sl-IEET 1 llllllllllllllll X IIIIIIHIHIY- J J. E. WOODS ETAL METHOD OF MAKING PERFORATED PLATES April 7, 1953 Filed July 6; 1945 2 SI'IEETS-SHEET 2 Patented p 7, 1953 5,Y-UNIT-ED STATES PATENT OFFICE I 2,633,630. I .1 METHOD OF MAKING PERFORATED PLATES 1 I v John .E. Woods, Cohasset, and Joseph- J. Mc- I i V Mahon,Lowell, Mass, assignors, by 'mesne assignments, to Standard-Thomson Corporation, Boston, Mass, a corporation of Delaware Application July 6, 1945, Serial No. 603,492

Present invention re lates to methods fof oods Patent No. 2,298,996 dated October 13,

n g. 1 'sja plan view. L jEiggjZj 1s aside elevation. F ig s. 3., 4, 5,. Gare plan views showing: the punched holes spacings. Fig.7 is a plan view of the holes before trueing. j Fig, 8 is an elevation of a trueing pin, Fig.9 is an elevation showing the trueing of the holes punched, v a

"Figs l0, ll are elevations showing the trueing operation. v

Fig,. l 2' is an elevation of. the product i V i Heat exchange apparatus of thatp type employs a yeryflarge number of closely spaced thin wall tubes. As an example, a typical oil cooler for aircraft may use about 2600 tubes, each of .210". outside diameter and spaced .250" on centers. Intheheader the. web of metal between adjacent tubesis 'thus only .040". The manufacture of header plates of such type is extrr-nnely difficult since, if the holes are punchedindividually or in sinall' g roups, the metal creepsso that it is im: possible to maintain accurate dimensions. On the other hand, punching of all of the holes at onetime is difficult because the punchesmust be solclolse together that adequate support cannot be provided .for them.

According to the present invention, the header platesare punched while flat with gang dies which substantiallyspan the entire area. The holes are punched-"in several, preferably forinoper'ations whereby inthe first punching operation a series of regular but widely spaced holes is formed and in the subsequent operations the spacesbetween the original holes are punched in regular order.

It has been'found that by this procedure. even though theholes are properly spaced on centers, the webs aredistorted and the holes formed in the original punching operation are partially closed up. Eiioits havebeen made to round and size the holes by reaming but this is slow and expensive. According to the present invention the plates are quickly and easily sized loy'stacking them in piles with loose pins extending through the holes. Starting with a single properly formed master sheet the successive sheets may be stacked with assurance that the pins will enter the holes and bring them to the proper size and spacing. Preferably a sheet to be used is removed from the dlholes," such as the header plates used in; r'al ators and oil coolers of the type described in 4"Claims." :(Cl. 29 1'63.5)

bottom of the stack, "a newsheet' tobe-sized is" placed on top andthe entire stack ,is-put ina' press whereby the pins 'areforced intothe holesof the new sheet The invention will be described in connection with a method of making headers approximately 11" in diameter and-having approximately -2600 holes each .210" in'diameter and spaced".250 on centers. The plate 6 from which the headers is formed is as shown in Fig. 1 originally-about 13 square and is provided at diagonally opposite corners with dowel holes 8 to line up the-plate for the several operations. The area within which the holes are to be punched is indicated by the dot-and-dash line boundary l0 in Fig.

If all the holes were to be punched i -one operation, the punches could not besatisfactorily supported because the space between them would be only about .040". Furthermore, as previouslyj stated, it is not satisfactory to punch the' h'ols individuallyor in small groups because the creep of the metal would make it impossible to maintain dimensions. Accordingly, the plate is punched in": four punching operations, each with a gang punch having approximately 650 individual punches.

In each operation, therefore, the holes are spaced on centers to afford sufficient space betweenadjacent punches for adequate support; "In the first punching operation shown in Fig. B'the holes are punched at the places indicated by the stip-' pled circles; in the second operation (Fig. 4) an-'; other set of holes is punched as indicated by'the plain circles; in the third operation (Fig. 5) the holes are punched as indicated by the circleswith stippled centers; and in the fourth operation (Fig. 6) the holes'are punchedas indicated by An elevationof a punch for one of the crosses. I operations is indicated diagrammatically in Fig. 2

wherein the plate is supported on a bed l2 and held in proper position by dowels l4. A gang punch it provided with individual is used for the punching operation.

Four separate punching operations with s'epa rate punches are preferred. It is possible to use a single punch and move the platewith relation to it for-the diiier'ent operations; but'some of the punches must be left off near the periphery; otherwise some holes would extend beyond the 1y deeme iadvaa a ei mpe a tiiafii i' l si that each punching operation encompasses the punches [8' are entire surface so that there is no tendency for metal creep which would distort the dimensions at the completion of the operation. The holes are spaced as indicated in the group shown in the upper part of Fig. 1 and in Fig. 6.

In all punching operations subsequent to the first, theholes and webs are necessarily distorted, even though the punched holes are properly located on centers. Thus, after the last operation, the holes which were punched. in preceding operations may be partly closed as, indicated in exaggerated way in Fig. '7. The hole formed in the last punching operation is shown in the center and the holes formed in preceding operations, are.

shown around it. Since many of the. holes are now out of round, the tubes could not be inserted into them. A reaming operation would be. slow and expensive and would further remove some of the metal of the webs and thus reduce the strength of the plate. According to the invention, a hole trueing and sizing operation is now performed. Previous to the sizing operation, however, a sheetis first run through a straightening or flattening machine of conventional form to; remove any waves or buckles that might have been occasioned by the punching operations.

The hole sizing operation is accomplished by stacking several plates over pins of special form, one-pin being used for each hole. As shown in Fig, 8, each pin 20 comprises a central body portion' 22- having an outside diameter corresponding to the proper hole size. Each pin has a tapered top end portion 24 of a length somewhat greater than the thickness of one sheet, and a shouldered bottom portion 26 of a length somewhat greater than the thickness of a sheet and of; a diameter considerably smaller than the body portion 22. It is necessary touse one pin for each, hole, that is, 2600 pins are necessary for the header design described herein. In Fig. there isshown a stack of seven plates. The body portions; of the, pins extend through the holes of the four bottom plates whilev the fifth plate has been engaged by the tapered portions 24 of the pins. The sixth plate is shown with the pins entering the holes, and a seventh plate may be placed on top. The four bottom plates have had their holes aligned and sized by the pins, and the upper plates are ready for alignment by the pins.- The stack is placed on the bed 30 of a press, the top plate being aligned with the stack by means of the dowels M, as shown in Fig. 9. The entire stack is then subjected to pressure by a ram. Inthe process of moving all of the plates downwardly in relation to the pins, the tapered portion of the pins find their way into the holes of the upper plate or plates as shown in Fig. 11. The bottom plate is freed from the pins because of the provision of the shouldered portions 26. Ehe bottom plate shown in Fig. 11 is now finished and may be removed after removing the stack from the dowels.

. Foreach sizing operation, therefore, one plate isapplied to the top of the stack, the stack is pressed, and the completely sized plate is thereafter removed from the bottom in a series of pressing operations, being advanced by an amount equal to its own thickness on each operation. Since the pins are the correct outside diameter for the formation of the holes, the holes are pressed out to proper shape and the webs are brought to uniform proper size. It will be understood thatthe portions 22 of the pins may be of any desired length and that the stack will be of a, corresponding height. It has been found satisfactory to use a pin length which will accommodate about four plates on the portion 22, as indicated in Figs. 10 and 11.

For this operation, it is necessary to start with a sheet in which the holes have been properly formed by reaming or any other suitable operation. After the process is oncestarted, however, the stack. forms its own. pin-locating means. It has been found that the dimensions are maintained true even after thousand of sizing operations. In other words, the positioning of the pins by previously formed plates and without any other centering or aligning means has been found adequate, to continue the sizing and aligning operation indefinitely.

Each plate, after having its holes thus sized, is cut on the line indicated at 3B in Fig. 1 and is formed with a flange 38 to form the completed header shown in Fig. 12. The tubes may then be inserted as described in the above mentioned Woods patent with assurance of proper tube spacing. It will be understood that a burr necessarily appears around each holeas a consequence. of the punching operation. In the hole-sizing;

operation a burr is pushed upwardly by the passage, of each plate over the pins. In theflanging operation for manufacture of the completed header, the flange is turned in such a. direction that the burrs are on the opposite side of the plate therefrom. That is to say, the burrs are on the inside of each header plate. Owin to proper sizing of the holes, the burrs do not interfere with the insertion of the tubes. It is preferable to have the burns on the inside surfaceof the header plates since if they were on the outside surface, they would interfere with the flow of brazing material by which the tubes are later secured to the headers as described in the Woods Patent No. 2,389,175, dated. November 20, 1945.

It will be seen that the present invention comprises two main features: first, the method of punching in several operations, with each operation encompassing substantially the entire area of the perforated sheet, and second, the sizing and trueing operation with individual pins. Although the punching method, as herein described, utilizes four operations, it may be carried out in any number ofv operations, depending on the number of holes; thus for a 24" header having about 10,000 holes, it has been found satisfactory to perform twelve operations, forming about 750 holes in each operation. In any case, it is important that the holes formed in any operation. be not localized in a part of the sheet, but that they be spaced to span or encompass the entire perforated area. In this way the dimensions of the sheet are preserved and the proper hole spacin is maintained. The fact that the hole spacing is maintained, even though some holes may be distorted in shape, makes it possible for the individual pins to enter the sheet for the hole sizing operation of Figs. 9 to 11.

Having thus described the invention, We claim:

1. A method of making perforated plates having a large number of closely spaced holes separated by narrow webs, which consists in forming the holes by punching, forming a stack of plates in which a sizing pin is inserted into each hole of each plate of the stack, each pin having a tapered portion at one end and a portion of reduced size at the other end, and compressing the stack to apply a new plate to the tapered portions of the pins and to free a trued plate at the reduced portions of the pins.

2. A method of trueing holes in perforated plates having a large number of close, regularly spaced punched holes separated by narrow Webs, which consists in forming a stack of plates with the holes in register, each hole of each plate having inserted therein a sizing pin having a central portion of correct diameter for hole sizing, each pin having a tapered portion at one end and a reduced portion at the other end, applying a, new plate over the tapered portions of the pins, and compressing the stack to cause the pins to enter the new plate and to free a trued plate from the pins at the reduced portions thereof.

3. A method of making perforated plates having a large number of closely spaced holes which consists in punching the holes in a series of operations in which the holes formed in each operation encompass substantially the entire area of the sheet, the holes for any single punching operation being spaced at distances greater than the ultimate hole spacing, the punching operations subsequent to the first forming holes in areas between the holes formed in preceding operations, whereby the sheet dimensions and the hole spacings are maintained, and trueing the holes by placing said sheet on a stack of similar previously formed sheets in which a sizing pin is received in each hole, each pin having a tapered portion for entry into a registering hole of the new sheet, each pin having a reduced portion at the end opposite the tapered portion, and compressing the stack to apply the new plate to the stack and to free a trued plate from the reduced portions of the pins.

4. A method of trueing holes in perforated plates having a large number of close, regularly spaced punched holes separated by narrow webs, which consists in forming a stack of plates with the holes in register, each hole of each plate having inserted therein a sizing pin having a central' portion of correct diameter for hole sizing, each pin having reduced end portions, applying a new plate to the stack with its holes in register with the pins, and compressing the stack to cause the pins to enter the new plate and to free a trued plate from the reduced portions at one end of the pins.

JOHN E. WOODS. JOSEPH J. MCMAHON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,062,995 Smith May 27, 1913 1,582,596 Grabo Apr. 27, 1926 1,967,202 Dalton July 17, 1934 2,260,182 Knutsen Oct. 21, 1941 2,295,078 Green Sept. 8, 1942 2,304,607 Sleeter Dec. 8, 1942 

